1. Field of the Invention
The present invention relates to an internal combustion engine, in which fuel injected from a fuel injection valve is supplied into a combustion chamber through an intake port.
2. Description of Related Art
In a known internal combustion engine of a port-injection type, fuel is injected from a fuel injection valve into an intake port, which opens to a combustion chamber of a cylinder, to supply the fuel through the intake port. For example, Japanese Unexamined Patent Publication No. 2004-353463, Japanese Unexamined Patent Publication No. 2003-262175, Japanese Unexamined Patent Publication No. H07-133752 (corresponding to U.S. Pat. No. 5,829,408), and Japanese Unexamined Patent Publication No. 2006-125333 disclose structures and control apparatuses of such an internal combustion engine.
Normally, in a case where the combustion chamber of the cylinder is communicated with a plurality of intake ports, the intake ports are branched from an intake passage at a branching point. In this case, when fuel is injected from a fuel injection valve located on an upstream side of the branching point, the fuel may adhere to a partition wall, which partitions between the intake ports at the branching point. The fuel, which adheres to the partition wall, flows into the combustion chamber without being atomized. The fuel, which is not atomized, does not undergo complete combustion, so that unburnt hydrocarbons (HCs) are exhausted from the internal combustion engine. In order to address the above disadvantage, it has been studied to place a fuel injection valve in each intake port (i.e., two fuel injection valves in the two intake ports, respectively, in the case where the two intake ports are communicated with the combustion chamber) in a manner that avoids adhesion of the fuel to the partition wall at the branching point to limit direct contact of the fuel injected from each fuel injection valve to the partition wall.
However, it has been found that even in the case where the fuel injection valves are provided to the intake ports, respectively a certain amount of fuel may still adhere to the inner wall of the intake port located on a downstream side of the branching point. Even in this case where the fuel adheres to the inner wall of the intake port on the downstream side of the branching point, the adhered fuel flows into the combustion chamber without being atomized and is thereby exhausted as unburnt hydrocarbons from the internal combustion engine. Therefore, even when the fuel injection valves are provided to the intake ports, respectively, there may still exist the phenomenon of the increased content of the hydrocarbons in the exhaust gas and the deteriorated fuel consumption.
Furthermore, the intake port is normally directed toward the combustion chamber to have an air flow direction, which is tilted relative to an axial direction of the cylinder. The intake port may be curved to direct the air flow direction toward the central axis of the cylinder at a location adjacent to the opening of the combustion chamber. It has been found that the fuel tends to adhere to the inner wall surface of this curved portion.